Dostoyno yest

Greetings all, here, and I apologise for writing this enquiry in English. I can read cyrillic script, but know but the smallest of Russian grammar.

I sing in a parish church choir in England, and musically we are quite adventurous. I have in my possession a vocal score of a Russian anthem which I would love to be able to teach my fellow singers, including the proper words of a Russian anthem by D. (Dimitri?) Bortnynsky. It begins with the words (transliterated) Dostoyno yest, yako voi istinu, blazhiti Tya borogoditzu.

Can anyone here please give me the source (I think it is likely to be a Psalm)?

With a Russian text and the aid of a Russian-English dictionary, I'm sure I can make enough sense of it for our choir.

Hi Scholiast, it's Church Slavonic, and your answer (and translation) is to be found on the cpdl.org page here.

Note, it's bogoroditsu (Богородицу) not borogoditzu. (And interesting use of the adjective "meet", in the sense "it is right and fitting".)

And according to this (librarium.orthodoxy.ru) page and other web pages such as this (pravoslavie.ru) one, it's a prayer that can be said after any other prayers or act as part of the Orthodox liturgy, but it's not actually part of a psalm.

Many thanks to both correspondents, particularly to Enquiring Mind for correcting my error in transcription. It is handy to know (though of course not in the slightest surprising) that it's originally an Orthodox Greek hymn or prayer, rather than "native" Slavonic. And of course - silly me - I should have recognised the reference to the mater Boga, which rules it out from being a psalm.